Fluidized shale distillation



NOV. 18, C. E JAHNIG F'LUIDIZED SHALE DISTILLATION Filed June 2l, 1949:EF-f 0 a4 S /5 m2/1512"L l 72 -72 f FEED nafs" HOPPER. @f'f 52 Pa oa uc-rs "f' M ze 77 sanne/z 22 60d 60 S l l L2 l M2 s-' SRE W 24 8 /8 /6 lg9753; Ml- -Mr 92 l2 'f l0 E/ uTR/A-ron IJ# r'/ 20 l 3o T .94

a Am. s ,35 gq l Patented Nov. 18, 1952 FLUIDIZED- VSIIALE DISTILLATIONCharles E. Jalinig,` Red Bankg'Nf'J.,` assigner to l StandardY OilDevelopment Company, A a corporation of Delaware VApplication'June'21,1949, Serial No; 100,327-

(Cl. V2072-14,)

4 Claims. 1

The present-invention relates to the art of distilling oil-bearingminerals such-as oil shale, 4oil sands, tar sands and the like,maintainedl in the form of subdivided particles ina highly turbulentstate, iluidized by upwardly flowing gases `vto resembled a boilingliquid, wherein the fresh charge undergoes rapid disintegration to forman excessive amount of particles having sizes below a properly fluidizedrange. More particularly, the invention relates to improved means -iormaintaining properly iluidized beds of rsuch materialsduring-distillation.

Prior to the present invention, it'has been proposed to carry out thedistillation of oil shale in the form oi subdivided-solids varying inparticle size from a line powder up to rather large aggregates of, say,about 1A; in. diameter-in a highly turbulent'fluidized state. 'The heatrequired for distillation has been supplied either as sensible heat ofpreheatedV process materials,`by o indirect heat exchange ofA the-fluidizedbedwith suitable heating means, by combustionof combustibleshale `constituents within the retorting zone, or as sensible heat ofhot spent shalehigh'ly heated in a separate combustion zoneV` and`circulated to the fluidized bed in the retorting` zone. The principalproblem encountered `in all these operations arises as the result of thestrong tendency of ltheshale to disintegrate rapidly in the course ofthe distillation to particles having an extremely small size ofaboutO--ZO microns Which'is the unit particle size of the'shale'silt.

For example, Colorado shalewhen subjected to a fluid-type distillationquickly forms a mass containing about 6()y per cent of fineso'O-ZO`microns size, and this even if the shale is charged in rather coarseaggregates. Attrition further increases the proportion of these nes inthe .highly turbulent'or circulating solidsimasses. At the condition Vof`uid shale distillation such fines tend tobe entrained and carriedoverhead'by theifluidizing gases. This situation is further .aggravatedby relatively frequent localized spurts or jets of gasiiorm materialscaused in the uidized bed by the flashing of water and oilfrom the coldfresh shale dropped into the hot fluidized bed. Even gas-solidsseparators of normally highest eiliciency have been found inadequate tocope with this degree of solids entrainment. Aside from severe losses ofvaluable carbonaceousv constituents removed from the distillation zonewith these nes, the carry-over of excessive amounts of fines seriouslycomplicates liquid product recovery dueto heavy slurry formation anddetrimentally affects the fluidity of the'luidizecl bed which may berapidly converted into a dilute `The present Ainvention provides meansfor eilec- -tively counter-acting the detrimental effectsv of this typeofines entrainment.

In accordance with the present invention, in `its broadest aspect,losses of shale fines having particlesizes oft-20 microns from akluidized shale bed undergoing distillation, by entrainment andcarry-over of the iines in the fluidizing gases and gasiformdistillation products, may be materially reduced by obstructing theupward now of lthe gases and entrained solids above the interface of thefluidized bed and within the distillation zone in such a manner thatgasiform materials may pass the obstructionV completely while aproportion of the entrained solids is deilected back into thenuidizedbed. This obstruction may have the form. of `inclined orhorizontal offset baiiles. prescribing a zig-zag flot/'forl thesolids-in-gas suspension, or of a non-iluidizable stationary packinghavingirregular passageways, or thelike. However, in accordance with apreferred embodimenty of the invention, the obstruction has the form ofa horizontal perforated plate or grid capable of supporting a secondiluidized solids mass above that undergoing distillation.

All types of obstructions mentioned aoid the advantage oi returning aproportion of entrained nes' by deilection continuously to the shale bedundergoingdistillation and thusof reducing fines carry-over into theproduct recovery' system and. its detrimental effects. However, when agrid plate is used, permitting solid particles to penetrate theperforations, a second Iiuidized bedof particles will form above thegrid within a relatively short time of operation. Such fiuidized solidshave a strong capacity' for collecting ines of 'li-20 microns size uptola concentration oi about 30-50 per cent. A more specic and preferredembodiment of the invention provides, therefore, for the maintenance ofa fluidized bed of solids supported by `a horizontal grid plate abovethe interface of the liluidized shale bed undergoing distillation.

The formation of such a second iluidized bed by `direct carry-over ofparticles from the retorting bed may be. replaced or supplemented byvthe addition of subdivided solids by means other than immediatecarry-over from the retorting bed. The preferred embodiment of theinvention involves-the supply to the second bed of spent. shale whichhas been subjected to combustion in a separate combustion zone for thepurposes of generating the heat required for distillation.

The two' 'iluidized beds are preferably connected by a conventionaldowncomer pipe which permits flow of solids from the upper :Iluidizedbed to the lower retorting bed. In this manner, a substantial proportionof the solids carried over from the retorting bed into the second bedmay be returned to the retorting bed. In addition, part or all of theheat-carrying burned shale recirculated from a separate combustion zonemay be passed through the upper bed to the retorting bed and thus servethe dual purpose of preventing loss of shale lines from the distillationzone and supplying heat to the retorting bed.

Having set forth its objects and general nature, the invention will bebest understood from the following more detailed description whereinreference will be made to the accompanying drawing, the single gure ofwhich is a semi-diagrammatic illustration of a system suitable to carryout a preferred embodiment of the invention.

Referring now in detail to the drawing, the numeral I! designates amostly conventional distillation vessel or retort adapted for fluid-typeshale distillation and containing a iluidized shale bed M1 supported bya gas distributing device, such as grid I2, and having a well definedinterface L1. Above this interface a second perforated grid I4 isprovided. An overflow downcomer IS leads from a point above grid I4 to apoint below interface L1.

In operation, fresh coarse shale, which may have a particle size ofabout 4-50 mesh, may be supplied from feed hopper I through line I8 intothe space between interface L1 and grid I2. A uidizing gas, such assteam, product tail gas, other inert gas, CO2 and/or air, is suppliedthrough line 2b and grid I2 at such a rate that a linear superficial gasvelocity of about 0.5-3 ft. per second, suitable for fluidization, isestablished within bed M1. Bed M1 may be maintained at a distillationtemperature of about 850-1l00 F. by any of the conventional methodsdescribed above.

The fresh shale upon entering bed M1, undergoes distillation anddisintegrates rapidly. As a result, bed M1 may have a particle sizedistribution about as follows:

Size: Weight per cent 0-20 microns 55 20-80 microns l0 8f) microns, 35mesh l5 On 35 mesh 20 A portion of the entrained solids impinges on theimperforate portions of grid I4 and is thus returned to bed M1. Theremainder of the entrained solids penetrates the perforations of gridI4. Initially the fines of 0 20 microns size carried through grid I4 mayremain entrained in the gases and vapors and may be carried therein to agas-solids separator 22 in which a substantial proportion of theentrained nes, say, about '70- 90%, may be separated. The separatedfines may be returned to bed M2 via dip-pipe 24, gradually building upthereon until a second fluidized bed M2 having an interface L2 is formedabove grid I4. Thereafter, a major proportion of the lines penetratinggrid I4 is retained in bed Mz, the remainder being carried intoseparator 22. Equilibrium cf the system is established and maintained byoverflowing and returning solids from bed Mz Via downcomer I6 to bed M1and withdrawing spent shale from bed M1 through line 30. In this manner,about 80-99% of the solids leaving bed M1 entrained in gases and vaporswill be returned to bed M1 via downcomer I6.

As previously indicated, the invention has particular advantages whenused in connection with a system wherein hot spent shale is circulatedfrom a separate combustion zone to the retorting zone for the purposesof heat supply. A system specically adapted to the application of theinvention is illustrated in the drawing.

As shown in the drawing, a fluidized combustion zone or burner 50 isprovided in addition to the elements just described. Spent shalewithdrawn through line 30 from bed M1 may be passed to line 35 andsuspended therein in air sufficiently preheated to support combustion ofthe shale. The air is supplied at a rate sufficient to carry the spentshale through grid 52 into burner 5I), to burn part or all of the carbonolf the spent shale at a temperature about 50300 F. higher than that inretort IIJ, and to maintain a superficial gas velocity within burner 50of about 1-3 ft. per second, adequate to establish a lluidized mass M50of burning shale having an interface L50 within burner 50. The gascontaining entrained shale fines passes overhead from level L50 and maybe further handled in any desired manner.

Burned spent shale is withdrawn from bed M50 through line 6I) which maybe an aerated standpipe or the like and passed substantially at thetemperature of mass M50 to bed M2 in retort I0. The circulation rate ofhot shale through line 50 depends on the temperature differentialbetween burner 50 and bed M1, and upon the heat requirement in vesselI0. A ratio of burned, hot shale to fresh shale charged of about 5-20:1is usually adequate for the purposes of heat supply. Approximately thesame solids circulation rate is maintained in lines 39 and 35 toestablish equilibriurn. Excess solids may be withdrawn from burner 50through line 62.

The particle size distribution of the solids circulating through line 60may be about the same as that specified above for bed M1.

In addition to containing material coarser than 20 microns, theseparticles are relatively low in carbon or practically carbon-free andhave, therefore, a substantially lower gas buoyancy than the high carbonparticles of similar size which are entrained and carried overhead frombed M1. The burned shale particles supplied through line 60 to retort I0above grid I4 are, therefore, ideally suited `to form a well fluidized,relatively dense bed of solids, Mz, above grid I4, adapted to retainsubstantial proportions of fines entrained from bed M1 and penetratinggrid I4. The hot solids then flow through downcomer I6 to supply theheat required in retorting bed M1 and to repeat the cycle describedabove. As a result of the high circulation rate of hot lowcarbon solidsfrom burner 50, bed M2 will at all times consist predominantly ofparticles of suiliciently low gas buoyancy to retain an adequateproportion of the fines of 0-20 microns size entering bed M2 from bedM1. When operating in the manner last described, the fines concentrationof the effluent of retort Il! leaving through line 26 will besubstantially less than in the absence of a second bed M2.

As an alternative to the procedure described above, the system shown inthe drawing may be operated as follows.

Heater 50 may be divided by a second grid 'In into two sections with theburning taking place in the lower section. The hot flue gases from thislower section then pass up through grid 'I0 into a second dense phaseM70. The gases are cooled in this section, withdrawn through line 12 andused to supply the fresh shale to the system as follows.

Feed hopper l is replaced by hopper 'I5 from which the fresh charge maybe supplied to line 'l2 by any suitable means, such as a screw conveyorll. 'Ihe gases in line 'I2 are then used for conveying the shale feed toan elevated feed hopper 80. separators 82 may be located in the top ofelevated feed hopper 80 to remove entrained solids. The shale fromhopper 80 then ows through line 84 to bed M70 wherein it is preheated bythe flue gases penetrating grid 1D. The preheated shale may thereafterbe fed via lines 86 and I8 to bed M1 in retort l0.

The advantages of this type of ow are as follows. The flue gases arecooled immediately so that piping and equipment following the heater areat a low temperature. This avoids expansion problems and expensivematerials of construction. The feed shale is preheated by the flue gasesso that less burning is required and less air is used. The flue gasesare under suiilcient pressure to be used in conveying the feed shale tothe elevated feed hopper. This eliminates the necessity of compressingrecycle make gas for this purpose. A hindered settler is used as heatexchanger, thus eliminating expensive exchanger surface.

The system illustrated in the drawing permits of various modifications.Bed Mz may serve as a cracking zone for the distillation productsliberated in bed M1. Cracking may be controlled by the amount of hotburned shale introduced through line B9. For this purpose, a portion ofthe hot shale in line 60 may be fed directly to bed M1 through lines 6land I8. Instead of pass- ,ing all of the spent shale from line throughline directly to burner 50, any desired portion of the suspension ofspent shale in air may be passed from line 35 through line 90 to anelutriator 92 where shale of undesired particle size may be removedthrough line 94, the remainder being passed through line 96 to burner 50to be further treated as above described.

While most of the volatile components present ln the feed shale will berecovered by retorting in vessel l0, it has been found that furtherquantities of valuable products often can be obtained by further heatingto a higher temperature. For example, ammonia and light fuel gases canbe recovered by heating the spent shale from vessel l0 or vessel 50 totemperatures of the order of 12001800 F. Such heating may beaccomplished using indirect heating, or by recirculation of heatedsolids from a heater Vessel, or by direct injection of an oxygencontaining gas.

In many cases the spent shale rejected from the retorting system willstill contain appreciable amounts of combustible material. These spentsolids can be used as fuel, as for example in a boiler house. Moreover,they may be used for the generation of fuel gas o-r synthesis gas bycontacting with steam, and/or carbon dioxide at suitable conditions.Heat for this process can be supplied by solids recirculation from aheater vessel, or by direct injection or an oxygen containing gas.

Other modifications of the systems illustrated may appear to thoseskilled in the art without deviating from the spirit of the invention.

The above description and exemplary operations have served to illustratespecific embodiments of the invention but are not intended to belimiting in scope.

What is claimed is:

1. In the process of distilling oil-bearing minerals of the type of oilshale, which disintegrate lwhen subjected to distillation, in the formof a dense turbulent mass of subdivided solids fluidr ized by anupwardly flowing gasiform medium to forni a well defined interfacewithin a distillation zone, the improvement which comprises feeding saidoil-bearing minerals to said mass, obstructing the upward flow of saidmedium containing entrained solids within the distillation zone at alevel above said interface by an obstruction, which permits said mediumto flow upwardly over the entire height of said distillation zone pastsaid obstruction, forming a second fiuidized mass of solids within saidzone above said obstruction, continuously circulating retorted mineralparticles from said first-named mass to a separate fluid-type combustionZone, maintaining at least two superimposed fiuidized beds in saidcombustion zone, subjecting said retorted minerals to combustion in thelower one of said beds, pasing hot nue gases from said lower bed throughthe upper one of said beds, supplying fresh minerals to said upper bedto be dried and preheated therein by said flue gases, and passingpreheated minerals from said upper bed to said first-named iiuidizedmass.

2. The process of claim 1 in which volatile products of distillation aresubjected to cracking in said second mass.

3. The process of claim 1 in which ue gases produced in said combustionzone are used to lift fresh minerals to an elevated point.

4. The process of claim 1 in which solid combustion residue from saidlower one of said beds is returned to said second fluidized mass.

CHARLES E. JAHNIG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,396,036 Blanding Mar. 5, 19462,396,709 Lefer Mar. 19, 1946 2,420,542 Jahnig May 13, 1947 2,444,990Hemminger July 13, 1948 2,471,119 Peck et al May 24, 1949 2,480,670 PeckAug. 30, 1949 2,483,485 Barr Oct. 4, 1949 FOREIGN PATENTS Number CountryDate 586,992 Great Britain Apr. 10, 1947

1. IN THE PROCESS OF DISTILLING OIL-BEARING MINERALS OF THE TYPE OF OILSHALE, WHICH DISINTEGRATE WHEN SUBJECTED TO DISTILLATION, IN THE FORM OFA DENSE TURBULENT MASS OF SUBDIVIDED SOLIDS FLUIDIZED BY AN UPWARDLYFLOWING GASIFORM MEDIUM TO FORM A WELL DEFINED INTERFACE WITHIN ADISTILLATION ZONE, THE IMPROVEMENT WHICH COMPRISES FEEDING SAIDOIL-BEARING MINERALS TO SAID MASS, OBSTRUCTING THE UPWARD FLOW OF SAIDMEDIUM CONTAINING ENTRAINED SOLIDS WITHIN THE DISTILLATION ZONE AT ALEVEL ABOVE SAID INTERFACE BY AN OBSTRUCTION, WHICH PERMITS SAID MEDIUMTO FLOW UPWARDLY OVER THE ENTIRE HEIGHT OF SAID DISTILLATION ZONE PASTSAID OBSTRUCTION, FORMING A SECOND FLUIDIZED MASS